Stepped Drill Bit for Restoring Distorted CLT Fastener Holes
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Solution Overview
Problem
Pre-drilled holes in Cross Laminated Timber (CLT) panels often become distorted due to shifting wood layers, making it difficult to insert dowels and compromising the structural integrity by requiring excessive force or incomplete filling, which can lead to a weakened connection.
Innovation Solution
A drill bit with strategically sharpened and dulled cutting edges and flutes is used to clean up the openings without enlarging them, ensuring each section is concentric about a single axis, allowing for proper dowel insertion and secure fastening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pre-drilled holes are made in CLT panels during manufacturing, then the panels are prepared for fastener insertion, but the holes become distorted due to wood layer shifting, making dowel insertion difficult and compromising structural integrity
Solution Approach 1:
The drill bit performs preliminary cleaning action on the distorted holes before dowel insertion. By removing accumulated wood material and reshaping the hole walls, the bit restores the holes to their original cylindrical form, ensuring proper dowel fit without requiring excessive force
Solution Approach 2:
The drill bit changes the geometric parameters of the distorted holes by removing material and restoring concentricity. The bit transforms the non-cylindrical, shifted-hole geometry back into a proper cylindrical shape with correct dimensions, enabling reliable dowel insertion
2Ease of operation
If excessive force is applied to drive dowels into distorted holes, then dowel insertion is achieved, but the connection is weakened and structural integrity is compromised
Solution Approach 1:
The drill bit enables the holes to self-correct their distortion by mechanically removing the shifted wood material. The cleaning process allows the hole geometry to naturally return to its intended cylindrical shape, eliminating the need for forceful dowel insertion that would compromise connection strength
3Manufacturing precision
If the openings are cleaned to remove distorted wood material, then proper dowel alignment is achieved, but the hole dimensions may be enlarged
Solution Approach 1:
The drill bit applies cleaning action selectively to specific regions of the hole where wood material has shifted and accumulated. By targeting only the distorted portions near the hole entrance and intermediate sections, the bit restores concentricity without removing material from the critical bottom region where the dowel must seat properly
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The drill bit effectively reshapes the distorted openings to accommodate dowels, ensuring proper alignment and secure fastening without damaging the original hole dimensions, thereby maintaining the structural integrity of the CLT connections.
Implementation Method 1
The bit is designed with cutting edges and flutes to allow material to be shaved from the walls of the opening
Implementation Method 2
The bit is designed with cutting edges and flutes to allow material to be shaved from the walls of the opening
Data Source
AI summary
A drill bit for use with construction using cross laminated timbers (CLT) is provided. The bit has both sharpened and dull portions of the cutting element of the bit, so that it can clean-out an opening in the CLT that has been partially obscured by shifts in the laminated constituents of the CLT, without elongating or otherwise changing the shape of the fastener opening. The use of the bit is made at the construction site in fastener openings previously made and otherwise obscured, thereby allowing the quick assembly and construction of a structure made of CLT.